1. Field of the Invention
This invention pertains to the field of footwear.
2. Description of the Related Art
Typical footwear, particularly footwear for active use, has a sole and an upper. The upper includes a foot opening and a throat--an elongate opening that extends from the foot opening to a vamp. A tongue is located in the throat opening and a shoelace is laced through edges along the throat to provide a secure closure mechanism.
Such footwear is donned onto a foot by loosening the laces, spreading apart the foot opening and throat, holding the tongue out of the way and then inserting a foot through the opening into the footwear. The laces may then be tightened to secure the footwear onto the wearer's foot.
Donning footwear is a part of daily life for most people and it posses little difficulty. However, for parents, donning footwear on small children can be exasperating. Children are sometimes reluctant to hold still. The adult must hold the footwear open, hold the tongue out of the way and guide the child's foot into the footwear--difficult actions on a squirming child.
Other people also require assistance with putting on their footwear. For instance, people with limited leg mobility and people with infirmities such as Alzheimer's disease, often require assistance from others to don footwear.
U.S. Pat. No. 2,619,744 discloses a "foot enclosing device" intended for infants that includes a heel which opens to permit rear entry into the shoe. The shoe has side portions that meet at the heel. A flap overlies the side portions and secures the side portions in a closed position. When the flap is disengaged from the side portions and lowered, a child's foot may be inserted into the shoe through the now-open heel. This design appears to require that the adult use both hands to hold open the shoe sides while the foot is inserted. With both hands on the shoe, it is difficult to control a child's foot and position it for entry into the shoe.
Other U.S. patents also disclose footwear construction that appears to be intended to provide footwear that is easy to don. U.S. Pat. Nos. 5,481,814, 5,184,410, and 474,574 disclose footwear that have hinged soles and divided uppers. The U.S. Pat. No. 474,574 uses a pin hinge on the sole to allow the front to pivot relative to the rear. The U.S. Pat. No. 5,184,410 likewise discloses a hinge attached to the sole. The U.S. Pat. No. 5,481,814 provides a cut through a midsole and an outsole that acts as a hinge. Because the outsole is very flexible, it does not have sufficient bias force to hold the shoe in a closed arrangement on a wearer's foot. Accordingly, the U.S. Pat. No. 5,481,814 provides a metal biasing means with a tensioner (i.e., a spring) to urge the shoe closed.
Several deficiencies are noted in the prior art footwear. The '744 patent discloses a design that appears to require two hands to hold open to receive a foot. The U.S. Pat. Nos. 474,574 and 5,184,410 disclose designs that have a split sole with a ferroalloy mechanical hinge. The U.S. Pat. No. 5,481,814 discloses a design having a separated midsole and a hinge that is the outsole. To compensate for the weak closing force of the outsole hinge, the design of the U.S. Pat. No. 5,481,814 incorporates a metal biasing means.
The U.S. Pat. Nos. 5,481,814, 5,184,410, and 474,574 all incorporate hardware that is uncommon in active footwear. As such, the hardware increases difficulty of manufacture, and expense. Furthermore, footwear soles endure significant stresses during use, and locating hardware in the sole invites failures that affect footwear performance.
Many footwear designs permit the sole to flex in a manner to accommodate movement of the foot during ambulation. During supination, the toes remain on the supporting surface while the heel moves upward, thus flexing the foot in a manner that shall be referred to as adduction, because the foot is bending inward on itself.
U.S. Pat. No. 4,559,724 discloses flex grooves aligned with a medial metatarsal-phalanges joint line and a second metatarsal-phalanges joint line. These flex grooves allow the sole to move with the foot during supination. These grooves do not facilitate flexing the sole in a direction that is opposite adduction, that is flexing that corresponds to abduction of the foot.
Footwear soles behave like beams. When flexed in the direction of adduction, the top and bottom are in compression and tension, respectively. When the sole is flexed in abduction, the forces reverse, that is the top is in tension and the bottom is in compression. Because of the structure of soles, and the location of the upper being fixedly attached to an upper margin of the sole, the dynamics of flexing the sole in adduction and abduction are significantly different.